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There are basically two types of laboratory pipette:
- Air displacement
- Positive displacement
- Air displacement is adequate for any water based and non viscous fluids
- There is an air gap between the fluid and the plunger so there is no direct contact with the instrument
- The pipette can dispense either by forward or reverse pipetting techniques depending on the required accuracy and precision
- Depress plunger to first stop
- Immerse tip vertically into liquid and smoothly release the plunger
- Depress plunger button to first stop to dispense liquid into receiving vessel
- Depress button fully to second stop to expel the remaining liquid from the tip
- Depress plunger button to second stop
- Immerse tip vertically into the liquid and smoothly release plunger button
- Depress plunger to first stop only to release liquid into vessel
- Discard remaining liquid by depressing to second stop
- Pre- wet tip x 2 before dispensing
- Dip the tip 2-4mm into the liquid
- Smooth aspiration both touching and not touching the side wall, (sometimes used with micrototre plate assays)
- preferred for viscous, volatile or corrosive samples
- Direct contact between plunger and sample
- Works by replacing both plunger and capillary for each sample
- Liquid is forced out by the plunger through the capillary when dispensing
- best for small volume precious samples